Bleaching and dyeing; fluid treatment and chemical modification – Reactive dye composition – process – or product
Patent
1992-03-18
1993-09-21
Clingman, A. Lionel
Bleaching and dyeing; fluid treatment and chemical modification
Reactive dye composition, process, or product
8549, 8618, 8918, 8917, B01D 1500, C02F 128, D06P 138, D06P 502
Patent
active
052464679
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to the post washing of dyed textiles. Textile surfaces are treated with reactive dyes, these contain a chromophore and a reactive site, but a proportion of the dye remains loosely bound to the textile surface and has to be removed by washing.
BACKGROUND TO THE INVENTION
Reactive dyes are widely used in the treatment of cotton, wool and regenerated cellulose because good fastness is achieved with a wide range of shades. After the dyeing stage it is necessary to remove the unreacted dye from the textile to ensure all the dye remaining on the textile surface is fast.
This washing stage is a lengthy process because a number of separate washing baths have to be used in sequence to ensure the final stage removes the remnants of dye only loosely bound to the surface. Thus the washing procedure uses a considerable amount of water and chemicals added to the washing baths to assist dye removal. The baths are usually operated at a temperature in the range 60.degree. C. to 100.degree. C. and therefore considerable heat energy is required. An additional consideration is the large quantity of water which contains washed off dye and which has to be disposed of via an effluent system. Environmental requirements are becoming more restrictive on the discharge of water containing coloured material and there is, in any case, a poor visual impact on water courses by such discharge. The process of reactive dyeing and washing is described in "The Dyeing of Cellulosic Fibres" published Dyers Company Trust 1986.
GENERAL DESCRIPTION OF THE INVENTION
The invention provides a method of removing loosely bound reactive dye on a textile surface wherein the textile surface is immersed in an aqueous bath characterised by contacting the bath medium with a material capable of absorbing the dye suspended or dissolved in the medium.
A preferred absorbing material is a hydrotalcite-like material, such term includes the calcined material. Other examples of absorbent material will have surface absorption sites for anions.
Thus, the present invention utilises anion exchange materials related to a compound of the formula Mg.sub.6 Al.sub.2 (OH).sub.16 CO.sub.3.4H.sub.2 O known as hydrotalcite, and for convenience referred to hereinafter as hydrotalcite-like materials.
The hydrotalcite-like materials useful in this method of removing non bound dyes according to the present invention can be described by formula I below: either but not both of k and m or n and p can be zero and k+m+n+p=1. combination of anions of similar or differing y- and k+2m+3n+4p-2-zy=0 and x can range from 1 to 100.
Examples of the cations M in the above formula are Li.sup.+, Mg.sup.2+, Zn.sup.2+, Fe.sup.2+, Cu.sup.2+, Sn.sup.2+, Ca.sup.2+ and Sr.sup.2+. Suitable N cations include Al.sup.3+, Fe.sup.3+, Ti.sup.4+ and Sn.sup.4+.
Preferred divalent cations are Zn.sup.2+, Cu.sup.2+ or Mg.sup.2+ or a combination of these ions, or a combination with other divalent cations.
The anion A may be an inorganic or organic anion. Preferred inorganic anions A are Cl.sup.-, NO.sub.3.sup.-, SO.sub.4.sup.2-, CO.sub.3.sup.2- and OH.sup.-. Examples of organic anions are carboxylate ions such as citrate and stearate.
Examples of hydrotalcite-like materials of this invention are: ##STR1##
Preparation of hydrotalcite-like compounds is known and has been described in a number of publications including Solid State Ionics 22 (1986) pages 135-141 where there is published a paper by Walter T Reichle entitled "Synthesis of Anionic Clay Minerals (Mixed Metal Hydroxides, Hydrotalcite)" and Chemtech (January 1986) pages 58-63 where there is published a paper by Walter T Reichle entitled "Anionic Clay Minerals".
The applicants have found hydrotalcite-like materials of grain size less than 110 Angstrom can absorb colorants at a faster rate than materials with a grain size greater than 110 Angstroms. These finer grain size materials also have a grater absorbant capacity. Preferably the grain size is less than 100 Angstrom, more preferably between 40 and 100 Ang
REFERENCES:
patent: 4458030 (1984-07-01), Manabe et al.
H. Zollinger, "Color Chemistry", (VCH), 1987, p. 136.
E. R. Trotman, "Dyeing and Chemical Technology of Textile Fibres," Sixth Edition, (Wiley-Interscience) 1984, pp. 447-450 and 456.
Cockett Keith R. F.
Concannon Martin
Webb Maurice
Clingman A. Lionel
Unilever Patent Holdings B.V.
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